On 4 Jan 2012 the temperature ranged from a scorching 91 F at San Gabriel CA (latitude 34 N) to -55 F at McGrath AK (latitude 63 N), a difference of 146 degrees F across 29 degrees of latitude, or close to 5 deg F per degree of latitude, or 1 deg F per 12 nautical miles of latitude. Below is the 500 hPa map for 12 UTC 4 Jan 2012 showing a fair amount of temperature gradient off the west coast at that time separating the upper cold low over the Bering Sea from the warm ridge over California. By the way, McGrath is the upper air site in Alaska with a -38 deg C temperature at 500 hPa.